Leather-like sheety product and production method therefor

ABSTRACT

A leather-like sheet product comprising (a) a sheet layer ( 1 ) composed of a fiber assembly ( 1 ) of fine fibers and an elastic polymer (A) existent in a space between fibers of the fiber assembly ( 1 ), (b) a sheet layer ( 2 ) essentially composed of a fiber assembly ( 2 ) or composed of a fiber assembly ( 2 ) and an elastic polymer (C) existent in a space between fibers of the fiber assembly ( 2 ), and (c) an adhesive layer composed of an elastic polymer (B) for bonding together the sheet layer ( 1 ) and the sheet layer ( 2 ), wherein  
     (d) the fibers of the sheet layer ( 1 ) and the fibers of the sheet layer ( 2 ) penetrate in the adhesive layer at the respective interfaces, the fibers of the sheet layer ( 1 ) are existent in the adhesive layer in a state that they are substantially not bonded to the elastic polymer (B), and the fibers of the sheet layer ( 2 ) are existent in the adhesive layer in a state that they are substantially bonded or not bonded to the elastic polymer (B); and (e) the elastic polymer (B) is existent in the adhesive layer in a state that it is bonded to at least the elastic polymer (A) contained in the sheet layer ( 1 ) at the interface,  
     and a production process therefor.  
     According to the present invention, there is provided a leather-like sheet which has good balance between softness and buckling resistance like natural leather and is deformed round with fine wrinkles when it is bent.

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a novel leather-like sheetproduct which has excellent stay properties and yet excellent balancebetween softness and buckling resistance and to a production processtherefor. Particularly, it relates to a leather-like sheet productsuitable for use in furniture and shoes and to a production processtherefor.

[0003] 2. Prior Art

[0004] Thanks to recent improvement made in technologies for making afine fiber from a fiber in use, coagulating an impregnating resin andfinishing for leather-like sheet products, quality such as softness,durability against actual use and the grade of suede- or nubuck-likeappearance has been improved, whereby the leather-like sheet productsare now used in a wide variety of fields such as clothing, furniture andshoes. However, the leather-like sheet products are still unsatisfactoryin terms of a soft and tight feel equivalent to high-quality naturalleather.

[0005] To obtain a sheet product having a similar feel to naturalleather, processes for laminating together two separately produced sheetlayers are disclosed by JP-B 62-15673 and JP-B 62-38474 (the term “JP-B”as used herein means an “examined Japanese patent publication”).Although the obtained sheet product has a difference between front andrear sides, when it is soft as a whole, it lacks tightness and when ithas tightness, it is hard. Therefore, a sheet product as soft and tightas natural leather cannot be obtained by these processes. The processesinvolve such a problem that when a treating solution is coated in theform of a film, the obtained sheet product becomes too hard because aresin or fiber constituting the sheet product is dissolved in a solventand bonded. Further, when the amount of a component dissolved in thetreating solution is small on the adhesive surface, for example, a resincomponent of a sheet product which contains a large amount of a fiberand a small amount of an impregnating resin is dissolved and bonded,sufficient adhesive force is hardly obtained.

[0006] Meanwhile, when a soft substrate is produced, there is such aproblem that the feel and buckling resistance of the obtained productworsen and natural leather-like properties such as softness and rounddeformation with fine wrinkles when it is bent cannot be obtainedbecause the substrate is forcedly elongated by tension generated duringprocessing.

[0007] To solve the above problems, a fabric scrim and an elastomersheet of rubber may be inserted into an intermediate layer as areinforcement. However, when scrim is used, strength improves butanisotropy is seen in a weaving direction, whereby the obtained productcannot be round unlike natural leather. When the elastomer sheet isused, elastic recovery when it is greatly bent cannot be small andelastic recovery is large unlike natural leather.

[0008] Particularly in such an application field as furniture that use apart in a large area, a sheet product having a large width is now indemand to improve cutting yield. However, the width of a sheet productis limited by machining equipment in each step and the existingequipment is designed to produce a hard substrate. As a result, when asoft substrate is to be produced, the substrate is elongated in lengthand shrunk in width by tension in a lengthwise direction, thereby makingit possible to produce only products having a small width. To produce aproduct having a large width, a huge amount of investment is needed tomodify the equipment to increase the width and reduce tension inaddition to the solving of the above quality problems. Therefore, aproduction process for a sheet product having soft substrate withoutreducing its quality as well as suppressing the shrinkage in widthduring processing has been strongly desired.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention which has been made inview of the above problems of the prior art to provide a leather-likesheet product which has excellent stay properties like natural leatherand yet excellent balance between softness and buckling resistance andis deformed round with fine wrinkles when it is bent as well as aproduction process therefor.

MEANS FOR SOLVING THE PROBLEMS

[0010] According to researches conducted by the inventors of the presentinvention, it has been found that the above object of the presentinvention is attained by a leather-like sheet product which comprises(a) a sheet layer (1) composed of a fiber assembly (1) of fine fibersand an elastic polymer (A) existent in a space between fibers of thefiber assembly (1), (b) a sheet layer (2) essentially composed of afiber assembly (2) or composed of a fiber assembly (2) and an elasticpolymer (C) existent in a space between fibers of the fiber assembly(2), and (c) an adhesive layer, composed of an elastic polymer (B), forbonding together the sheet layer (1) and the sheet layer (2), wherein

[0011] (d) the fibers of the sheet layer (1) and the fibers of the sheetlayer (2) penetrate in the adhesive layer at the respective interfaces,the fibers of the sheet layer (1) are existent in the adhesive layer ina state that they are substantially not bonded to the elastic polymer(B), and the fibers of the sheet layer (2) are existent in the adhesivelayer in a state that they are substantially bonded or not bonded to theelastic polymer (B); and (e) the elastic polymer (B) is existent in theadhesive layer in a state that it is bonded to at least the elasticpolymer (A) contained in the sheet layer (1) at the interface.

[0012] Researches conducted by the inventors of the present inventionhave revealed that the leather-like sheet product of the presentinvention can be obtained by the following production process.

[0013] That is, according to the present invention, there is provided aprocess for producing a leather-like sheet product comprising the stepsof:

[0014] bonding together a sheet layer (1′) composed of a fiber assemblyof sea-island type fibers made from a mixture of at least two differentpolymers which differ from each other in solvent solubility and anelastic polymer (A) existent in a space between fibers of the fiberassembly and a sheet layer (2) essentially composed of a fiber assembly(2) or composed of a fiber assembly (2) and an elastic polymer (C)existent in a space between fibers of the fiber assembly (2) by anadhesive layer composed of an elastic polymer (B); and

[0015] treating the laminated sheets with a solvent which does notdissolve the island component of the sea-island type fiber and theelastic polymers but dissolves the sea component of the sea-island typefiber to dissolve and remove the sea component in order to make a finefiber from the sea-island fiber.

EMBODIMENT OF THE INVENTION

[0016] The leather-like sheet product and production process therefor ofthe present invention will be described in detail hereinbelow.

[0017] The leather-like sheet product of the present inventionsubstantially comprises a sheet layer (1) and a sheet layer (2) both ofwhich are bonded together by an adhesive layer composed of an elasticpolymer (B).

[0018] The sheet layer (1) of the present invention is composed of afiber assembly (1) of fine fibers and an elastic polymer (A) existent ina space between fibers of the fiber assembly (1) and preferably containsa resin which comprises as an essential ingredient a high-molecularelastic polymer in a space between fibers of a finely entangled nonwovenfabric which is entangled inform of three dimensions.

[0019] The fine fiber is a fine fiber of 0.5 dtex or less, preferably0.1 dtex or less, or a bundle of fine fibers of 0.5 dtex or less,preferably 0.1 dtex or less. Stated more specifically, it is (i) a finefiber of 0.5 dtex or less obtained by spinning independently, or (ii) afine fiber obtained by removing at least one component of amulti-component fiber obtained by spinning a polymer compositionconsisting of two or more components which differ from each other insolvent solubility by composite spinning or blend spinning as asea-island type fiber, or a fine fiber obtained by splitting a compositefiber having a laminated section. To obtain a non-bonding structure withthe elastic polymer (B) to be treated later, the surface of the fibermay be treated with a sizing agent such as silicone or polyvinylalcohol. As for a preferred combination of components of a polymercomposition consisting of two or more components which differ from eachother in solvent solubility, when a polyester is selected as aninsoluble component, a polyolefin such as polyethylene, polypropylene orpolystyrene is preferably selected as an easily soluble component andwhen a polyamide is selected as an insoluble component, a polyester orpolyolefin is preferably selected as an easily soluble component.

[0020] To obtain a fiber assembly of these fibers, a known card, layer,needle rocker or fluid (water jet) entangling machine is preferably usedto produce a finely entangled nonwoven fabric having a high density ofentangled fibers.

[0021] In the sheet layer (1) of the present invention, the elasticpolymer (A) existent in a space between fibers of the fiber assembly isa polyurethane-based elastomer such as polyurethane elastomer, polyureaelastomer or polyurethane-urea elastomer, polyester-based elastomer,synthetic rubber, natural rubber or polyacrylic acid resin, out of whicha polyurethane-based elastomer is preferred. For example, thepolyurethane-based elastomer is obtained by reacting a polyol with anorganic diisocyanate in the presence of a low-molecular weight chainextender. That is, the polyurethane-based elastomer is obtained byreacting a polyol having a molecular weight of 500 to 4,000 such aspolyethylene glycol, polypropylene glycol, polytetramethylene glycol,polybutylene carbonate, polyhexamethylene carbonate, polyethyleneadipate, polybutylene adipate or polyhexamethylene adipate with anorganic diisocyanate such as diphenylmethane diisocyanate, tolylenediisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethanediisocyanate or 3,3,5-trimethyl-5-isocyanatemethylcyclohexyl isocyanatein the presence of a low-molecular weight chain extender such asethylene glycol, butylene glycol, xylylene glycol, propylenediamine,hexamethylenediamine, 4,4′-diaminodiphenylmethane,3,3,5-trimethyl-5-aminomethylcyclohexylamine,4,4′-diaminodicyclohexylmethane, hydrazine, amino acid hydrazide ordicarboxylic acid hydrazide. The hardness of the elastic polymer (A) ispreferably 100 to 3,000 N/cm², more preferably 300 to 1,500 N/cm², themost preferably 400 to 1,000 N/cm² in terms of 100% elongation stress ofa film formed from the elastic polymer (A) alone.

[0022] To make the elastic polymer (A) existent in the fiber assembly,the fiber assembly is treated with an organic solvent solution oraqueous dispersion of the elastic polymer (A) and then the solution iscoagulated on the fiber assembly by a conventionally known wetcoagulation process or dry coagulation process. Any compounding agentssuch as a porosity controlling agent and colorant may be added to thetreating solution in limits that do not impair the elasticity of theelastic polymer (A). Since the softness and elastic recovery of thesheet product are adjusted by the amount of the elastic polymer (A)deposited on the fiber assembly, the amount of the elastic polymer ispreferably 10 to 120 wt %, more preferably 25 to 80 wt % based on thefiber assembly.

[0023] A grain layer composed of an elastic polymer or a napped layer offine fibers may be formed on the surface (surface opposite to thesurface to which the sheet layer (2) is bonded) which is the exteriorside of a leather-like sheet product of the sheet layer (1) by aconventionally known method. The elastic polymer of the grain layer maybe porous or non-porous, or a single layer or laminate. The formation ofthe grain layer or napped layer may be carried out before or after thestep of bonding the sheet layers by the adhesive layer composed of theelastic polymer (B).

[0024] The thickness and density of the sheet layer (1) of theleather-like sheet product of the present invention are preferably asfollows. First, the thickness t₁ (mm) of the sheet layer (1) ispreferably 0.2 to 1.5 mm, more preferably 0.3 to 1.3 mm. When thethickness is smaller than 0.2 mm, the layer is too thin and not strongenough, or may be difficult to be processed substantially. When thethickness is larger than 1.5 mm, the layer is too thick, has a hard feeland may be limited in application. Further, the apparent density pi(g/cm³) of the sheet layer (1) is preferably 0.20 to 0.48 g/cm³, morepreferably 0.25 to 0.45 g/cm³. When the apparent density of the sheetlayer (1) is smaller than 0.20 g/cm³, the layer has a soft feel but nottight feel and may not be strong enough. When the apparent density islarger than 0.48 g/cm³, the layer may have a hard feel.

[0025] A description is subsequently given of the sheet layer (2) of theleather-like sheet product of the present invention. The sheet layer (2)is composed of a fiber assembly (2) and an elastic polymer (e) existentin a space between fibers of the fiber assembly (2). The fibersconstituting the fiber assembly (2) of the sheet layer (2) may beordinary fibers, for example, natural fibers such as cotton, flax orwool fibers, chemical fibers such as rayon, nylon, polyester orpolyurethane fibers, or blend fibers thereof. The fiber assembly may bea fabric such as a knitted fabric other than a entangled nonwovenfabric. In order to obtain a non-bonding structure with the elasticpolymer (C), it is preferred to treat the surface of the fiber with asizing agent such as silicone or polyvinyl alcohol in advance or to usea sea-island type fiber from which a sea component can be removed afterthe sheet layers (1) and (2) are bonded together. It is also preferredto impregnate the fiber with a resin which contains the elastic polymer(C) as an essential ingredient. The amount of the elastic polymer ispreferably 2 to 120 wt %, more preferably 10 to 80 wt % based on thefiber assembly (2). Further, the sheet layer (2) is preferably composedof a fiber assembly of fine fibers and the elastic polymer (C) existentin a space between fibers of the fiber assembly like the sheet layer(1). The elastic polymer (C) is identical to the above elastic polymer(A) used in the sheet layer (1).

[0026] A grain layer composed of an elastic polymer or a napped layer offine fibers may be formed on the surface (surface opposite to thesurface to which the sheet layer (1) is bonded) which is the exteriorside of a leather-like sheet product of the sheet layer (2) by aconventionally known method like the sheet layer (1).

[0027] The thickness and density of the sheet layer (2) are preferablyas follows. First, the thickness t₂ (mm) of the sheet layer (2) ispreferably 0.2 to 2.5 mm, more preferably 0.3 to 2.0 mm. When thethickness is smaller than 0.2 mm, the layer is too thin and not strongenough, or may be difficult to be processed substantially. When thethickness is larger than 2.5 mm, the layer is too thick, has a hard feeland may be limited in application. Further, the apparent density ρ₂(g/cm³) of the sheet layer (2) is preferably 0.20 to 0.48 g/cm³, morepreferably 0.23 to 0.45 g/cm³. When the apparent density of the sheetlayer (2) is smaller than 0.20 g/cm³, the layer has a soft feel but nottight feel and may not be strong enough. When the apparent density islarger than 0.48 g/cm³, the layer may have a hard feel.

[0028] The thicknesses and densities of the sheet layer (1) and thesheet layer (2) preferably satisfy the following expressions (1) to (6)at the same time.

0.20≦ρ₁≦0.48  (1)

0.20≦ρ₂≦0.48  (2)

0.5≦ρ₁/ρ₂≦2.4  (3)

0.2≦t₁≦1.5  (4)

0.2≦t₂≦2.5  (5)

0.4≦(t ₁ +t ₂)≦4.0  (6)

[0029] Out of the above expressions, the expressions (1), (2), (4) and(5) show the thicknesses t₁ and t₂ (mm) and apparent densities ρ₁ and ρ₂(g/cm³) of the sheet layer (1) and the sheet layer (2), respectively.

[0030] Further, the expression (6) shows the total (t₁+t₂) of thethickness t₁ (mm) of the sheet layer (1) and the thickness t₂ (mm) ofthe sheet layer (2), which is preferably 0.4 to 4.0, more preferably 0.4to 3.6. When (t₁+t₂) is smaller than 0.4, these layers are too thin andnot strong enough, and may be difficult to be laminated together. When(t₁+t₂) is larger than 4.0, these layer are too thick, have a hard feeland may be limited in application. Further, the expression (3) shows theratio ρ₁/ρ₂ of the apparent density ρ₁ (g/cm³) of the sheet layer (1) tothe apparent density ρ₂ (g/cm³) of the sheet layer (2), which ispreferably 0.50 to 2.4, more preferably 1.00 to 2.0, particularlypreferably 1.05 to 2.00. When ρ₁/ρ₂ is smaller than 0.50 or larger than2.4, a dense feel of a low-density side decreases, the number ofwrinkles may increase and a sense of difference is easily given due to abig difference in density.

[0031] The sheet layers (1) and (2) may be produced by preparing twothick sheets and slicing them into two or more layers or by slicing asingle thick sheet. Since a thin nonwoven fabric having a thickness of 1mm or less generally has low strength and low processability and cannotincrease the line speed, its productivity is low. Therefore, it ispreferred to form a thick sheet and slice it into the sheet layers (1)and (2) having a desired thickness.

[0032] The sheet layer (1) and the sheet layer (2) are bonded togetherby the adhesive layer composed of the elastic polymer (B). To bondtogether the sheet layer (1) and the sheet layer (2), an organic solventsolution or aqueous dispersion of the elastic polymer (B) is applied tothe surface of one of the sheet layers and the coated sheet layer islaminated with the other sheet layer. The coating solution may containvarious additives in limits that do not impair bonding. The amount ofcoating which depends on permeability into the substrate is preferably20 to 500 g/m² in terms of dry weight.

[0033] The elastic polymer (B) for forming this adhesive layer may be anelastic material of a polyurethane resin, polyacrylic acid resin,synthetic rubber or polyvinyl acetate resin. Out of these, thepolyurethane resin is the most preferred from the viewpoint of theapplication of the leather-like sheet product of the present invention.The polyurethane resin is obtained by reacting a polyol with an organicdiisocyanate in the presence of a low-molecular chain extender as willbe described hereinafter. That is, the polyurethane resin is obtained byreacting a polyol having a molecular weight of 500 to 4,000 such aspolyethylene glycol, polypropylene glycol, polytetramethylene glycol,polybutylene carbonate, polyhexamethylene carbonate, polyethyleneadipate, polybutylene adipate or polyhexamethylene adipate with anorganic diisocyanate such as diphenylmethane diisocyanate, tolylenediisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethanediisocyanate or 3,3,5-trimethyl-5-isocyanatemethylcyclohexyl isocyanatein the presence of a low-molecular chain extender such as ethyleneglycol, butylene glycol, xylylene glycol, propylenediamine,hexamethylenediamine, 4,4′-diaminodiphenylmethane,3,3,5-trimethyl-5-aminomethylcyclohexylamine,4,4′-diaminodicyclohexylmethane, hydrazine, amino acid hydrazide ordicarboxylic acid hydrazide. Further, it is preferred to use apolyfunctional isocyanate obtained by an addition reaction betweentolylene diisocyanate or diphenylmethane diisocyanate and trimethylolpropane as an organic isocyanate to obtain a crosslinked polyurethaneresin in order to improve adhesion strength and solvent resistance. Inthis case, after the polyurethane resin is applied to any one of thesheet layers while it is not crosslinked and the sheet layers (1) and(2) are laminated together, aging is carried out until crosslinking endsto complete bonding. To shorten the aging time, various catalysts may beadded to the coating solution.

[0034] The adhesive layer in the present invention means not only alayer composed of the elastic polymer (B) alone but also a layer havinga higher density than other portions of the sheet layers which do nottake part in bonding due to the existence of the elastic polymer (B) insome of spaces in the sheet layers (1) and (2). In the presentinvention, it is preferred that a layer composed of the elastic polymer(B) alone should not exist although there is an adhesive layer betweenthe sheet layers (1) and (2). The average thickness of the adhesivelayer composed of this elastic polymer (B) is preferably 0.01 to 0.5 mm.As for the physical properties of a film formed from this elasticpolymer (B) alone, the 100% elongation stress of the film is preferably200 to 3,000 N/cm². The coating solution preferably contains alow-density substance such as air. In this case, the apparent density ofa sheet formed from the coating solution is preferably 0.5 to 0.8 g/cm³.When values of these characteristic properties are below their lowerlimits, such a problem as insufficient adhesion strength easily arises.When the values are beyond their upper limits, the feel tends to behard.

[0035] In the adhesive layer of the present invention, although fibersof the sheet layer (1) and fibers of the sheet layer (2) penetrate inthe adhesive layer at the respective interfaces, the fibers of the sheetlayer (1) are existent in a state that they are substantially not bondedto the elastic polymer (B), the fibers of the sheet layer (2) areexistent in a state that they are substantially bonded or not bonded tothe elastic polymer (B), and further in the adhesive layer, the elasticpolymer (B) is existent in a state that it is bonded to at least theelastic polymer (A) contained in the sheet layer (1) at the interface.

[0036] As described above, in the present invention, the elastic polymer(B) must be existent in the adhesive layer in a state that it issubstantially not bonded to the fibers constituting the sheet layer (1).Meanwhile, the elastic polymer (B) may be bonded or not bonded to thefibers constituting the sheet layer (2) but preferably not bonded to thefibers.

[0037] The state that the elastic polymer (B) of the layer of theelastic polymer (B) is substantially not bonded to the fibers is a statethat fine fibers or ordinary fibers which are not in contact with theelastic polymer (B) or not bonded to the elastic polymer (B) even whenthey are in contact with the elastic polymer (B) account for at least50% or more, preferably 80% or more, more preferably 95% or more of thetotal of all the fibers in the section of the sheet. Further, when abundle of fine fibers is used as some of the fibers of the sheet layer,it is preferred that the elastic polymer (B) should not exist in theinside space of the bundle of fine fibers and should not be in contactwith fine monofilaments contained in the bundle of fine fibers althoughthe bundle of fine fibers penetrates in the elastic polymer (B) of theadhesive layer.

[0038] This structure is obtained by the following method, for example.That is, the sheet layer (1) composed of a sea-island type fiber fromwhich a fine fiber can be made is formed, bonded by the adhesive layercomposed of the elastic polymer (B), and treated with a solvent whichdoes not dissolve the island component of the fine fiber and the elasticpolymers of the sheet layers and the layer of the elastic polymer (B)and selectively dissolves the sea component of the fiber to remove thesea component of the sea-island type fiber. By this method, the seacomponent around the sea-island type fiber is dissolved and removed,whereby a structure that the elastic polymer (B) is not bonded to thefine fiber of the island component is formed though the elastic polymer(B) in the adhesive layer composed of the elastic polymer (B) is bondedto the elastic polymer (A) or (C) of the sheet layer. In this case, theelastic polymer (A) is not bonded to the fine fiber of the islandcomponent in the sheet layer as well, thereby improving a feel.

[0039] It is further preferred that the sheet layer (2) should becomposed of a fiber assembly of sea-island type fibers made from atleast two different polymer compositions which differ from each other insolvent solubility and the elastic polymer (C) existent in a spacebetween fibers of the fiber assembly, like the sheet layer (1). Sincethe fine fiber of the island component of each of the sheet layers (1)and (2) is not bonded to the elastic polymers (A), (B) and (C) in thiscase, a structure that all the elastic polymers of the leather-likesheet product are not bonded to the fine fibers is thus formed.

[0040] Other methods for bonding not to the fiber but to other elasticpolymer include one in which the surface of the fiber is treated with asilicone-based softening water repellent to prevent bonding between theelastic polymer and the fiber before the elastic polymer is applied andone in which a substance between the elastic polymer and the surface ofthe fiber is removed after the elastic polymer is bonded to otherelastic polymer. The substance to be removed is a polyvinyl alcohol whenthe surface of the fiber is treated with the polyvinyl alcohol inadvance or a sea component when a sea-island type fiber is used as theabove fiber.

[0041] The elastic polymer (B) of the adhesive layer is preferablybonded to the elastic polymer (A) of the sheet layer (1) and the elasticpolymer (C) of the sheet layer (2) which is impregnated with a resin atthe respective interfaces to increase adhesive force between the sheetlayer (1) and the sheet layer (2).

[0042] The leather-like sheet product of the present invention ispreferably the following sheet product (I) or (II):

[0043] (I) A leather-like sheet product comprising (a) a sheet layer (1)composed of a fiber assembly (1) of fine fibers and an elastic polymer(A) existent in a space between fibers of the fiber assembly (1), (b) asheet layer (2) composed of a fiber assembly (2) of fine fibers and anelastic polymer (C) existent in a space between fibers of the fiberassembly (2), and (c) an adhesive layer, composed of an elastic polymer(B), for bonding together the sheet layer (1) and the sheet layer (2),wherein

[0044] (d) the fibers of the sheet layer (1) and the fibers of the sheetlayer (2) penetrate in the adhesive layer at the respective interfaces,the fibers of the sheet layer (1) are existent in the adhesive layer ina state that they are substantially not bonded to the elastic polymer(B), and the fibers of the sheet layer (2) are existent in the adhesivelayer in a state that they are substantially not bonded to the elasticpolymer (B); and (e) the elastic polymer (B) is existent in the adhesivelayer in a state that it is bonded to the elastic polymer (A) containedin the sheet layer (1) at the interface and to the elastic polymer (C)contained in the sheet layer (2) at the interface

[0045] (II) A leather-like sheet product comprising (a) a sheet layer(1) composed of a fiber assembly (1) of fine fibers and an elasticpolymer (A) existent in a space between fibers of the fiber assembly(1), (b) a sheet layer (2) composed of a fiber assembly (2) of finefibers and an elastic polymer (C) existent in a space between fibers ofthe fiber assembly (2), and (c) an adhesive layer, composed of anelastic polymer (B), for bonding together the sheet layer (1) and thesheet layer (2), wherein

[0046] (d) the fibers of the sheet layer (1) and the fibers of the sheetlayer (2) penetrate in the adhesive layer at the respective interfaces,the fibers of the sheet layer (1) are existent in the adhesive layer ina state that they are substantially not bonded to the elastic polymer(B), and the fibers of the sheet layer (2) are existent in the adhesivelayer in a state that they are substantially bonded to the elasticpolymer (B); and (e) the elastic polymer (B) is existent in the adhesivelayer in a state that it is bonded to at least the elastic polymer (A)contained in the sheet layer (1) at the interface and to the elasticpolymer (C) contained in the sheet layer (2) at the interface.

[0047] The leather-like sheet product of the present inventionpreferably has a leather-likeness index of 0.5 to 2.0. The term“leather-likeness index” is a value calculated from the followingequation by measuring flexural resistance (RB), compressive stress (P3)and elastic recovery (ER) in accordance with measurement methods whichwill be described hereinafter.

leather-likeness index=compressive stress(P3)/(flexuralresistance(RB)×elastic recovery(ER))

[0048] As for the meaning of the leather-likeness index, as this valuebecomes greater, the product is softer and has larger compressive stress(higher tightness) and smaller elastic recovery. A largeleather-likeness index means that the product has properties closer tonatural leather.

[0049] To increase the leather-likeness index, flexural resistance (RB)and elastic recovery (ER) must be reduced and compressive stress (P3)must be increased. For example, in order to reduce the flexuralresistance (RB) of the sheet product of the present invention, it ispreferred that the elastic polymer (A) and the elastic polymer (C)should be existent in states that they are not bonded to the fibers ofthe sheet layer (1) and the fibers of the sheet layer (2), respectively,and that the elastic polymer (B) of the adhesive layer should interposebetween the sheet layer (1) and the sheet layer (2). In order toincrease compressive stress (P3), it is preferred that the apparentdensities of the sheet layer (1) and the sheet layer (2), the thicknessof the adhesive layer and the modulus of the resin should be set to theabove appropriate values. Further, in order to reduce elastic recovery,it is preferred that the elastic polymer (A) and the fiber assembly inthe sheet layer (1) should not be bonded to each other and/or theelastic polymer (C) and fibers in the sheet layer (2) should not bebonded to each other.

[0050] Further, when the leather-like sheet product of the presentinvention is to be used in shoes, the peel strength of the surface ofthe sheet product is preferably 20 N/cm or more, more preferably 25 N/cmor more. This peel strength is a value per 1 cm in width of peelstrength obtained by laminating together two 2.5 cm×9.0 cm sample piecesby a polyurethane adhesive in such a manner that their front surfacesbecome adjacent to each other and by making a peel test on the obtainedlaminate. In order to obtain satisfactory peel strength, it is importantto fully increase the density of entangled fibers in a thicknessdirection of the fibers in the width of the sheet layer. For example, itis achieved by an effective fiber density obtained by a needle punchingor fluid (water jet) entangling method. It is also important to improveadhesive force between the sheet layer (1) and the sheet layer (2) bythe elastic polymer (B). For example, the elastic polymer (B) of theadhesive layer may be infiltrated into the sheet layer (1) and the sheetlayer (2).

[0051] The surface of this leather-like sheet product may be napped by aconventionally known method, provided with a grain layer, dyed or thelike. Although these treatments may be carried out in any step, they maybe carried out after the sheet layers are bonded together by theadhesive layer to avoid the deformation of the substrate caused bytension. For example, when the surface is to be napped, it Is preferredto buff and dye the product in the final step so as to protect the softsheet and fine nap. When a grain surface structure is to be provided, itis effective to form a porous elastic polymer layer upon theimpregnation of the surface of the sheet layer with the elastic polymerand/or to form a non-porous elastic polymer layer by coating in thefinal step. However, the present invention is not limited to these andthe order may be changed, or other embossing and rubbing steps may becombined.

[0052] The thus obtained leather-like sheet product has excellent stayproperties like natural leather and yet good balance between softnessand buckling resistance and is deformed round with fine wrinkles when itis bent and particularly suitable for use in furniture and shoes. Theprocess of the present invention is a production process whichsuppresses shrinkage in width during processing without reducing thequality of a soft substrate.

EFFECT OF THE INVENTION

[0053] The present invention provides a leather-like sheet producthaving leather-like properties with a large leather-likeness index inwhich a sheet layer (1) and a sheet layer (2) both containing a fiberassembly are bonded together by an adhesive layer composed of an elasticpolymer (B) so that the adhesive layer is existent as an intermediatelayer of the leather-like sheet product and functions as an intermediatelayer against the bending deformation of the sheet, and tensile stressand compressive stress (P3) upon large deformation can be made largewithout increasing flexural resistance (RB) and elastic recovery (ER)upon small deformation, compared with a sheet product composed of only afiber assembly and an elastic polymer without an adhesive layer.

[0054] There is a layer in which elongation deformation (portion curvedoutward) and compression deformation (portion compressed inward) do notoccur in a sheet when the sheet is deformed by bending in terms of thestrength of materials. The expression “intermediate layer” as usedherein means this layer.

[0055] Since flexural resistance is expressed by an integral value ofthe product of the distance from the intermediate layer and stress atthat position on the flexural section of the sheet, even if ahigh-modulus and high-density layer is existent near the intermediatelayer, flexural resistance (RB) upon small deformation is not impaired.

[0056] Meanwhile, since force for bending and compressing the sheetstrongly to increase bending deformation and compressive stress (P3)upon large deformation increase in proportion to density, a producthaving leather-like properties closer to natural leather having a softand tight feel can be obtained by the existence of an adhesive layerhaving a higher density than the sheet layers as an intermediate layer.

[0057] Further, since the elastic polymer (B) of the adhesive layerpenetrates in the sheet layer (1) but is not bonded to the fibers of thesheet layer (1), it is possible to obtain a leather-like sheet productretaining softness and adhesive strength.

[0058] Owing to the existence of this adhesive layer, elongation in alengthwise direction and shrinkage in a breadthwise direction caused bytension generated during processing can be suppressed in the steps afterbonding, in addition to the above excellent softness and bucklingresistance.

EXAMPLES

[0059] The following examples and comparative examples are provided forthe purpose of further illustrating the present invention but are in noway to be taken as limiting. Measurement values in the examples andcomparative examples were obtained by the following methods.

[0060] 1) Thickness

[0061] This was measured in accordance with the JIS K 6505 method exceptthat a measuring instrument having a flat and round pressure surfacewith a diameter of 10 mm and a pressure load of 11.8 KPa (120 gf/cm²)was used.

[0062] 2) Weight

[0063] This was obtained by measuring weight in accordance with the JISK 6505 method and calculating a value per 1 m² from the weight. The unitis g/m².

[0064] 3) Density

[0065] The apparent density was calculated from the above measurementvalues of thickness and weight.

[0066] 4) 5% Stress (Elongation Load), 20% Stress (Elongation Load),Tensile Strength, Elongation Stress

[0067] These were measured in accordance with the JIS K6505 method.

[0068] 5) Flexural Resistance (RB)

[0069] A 2.5 cm×9.0 cm sample piece was fixed to a fixing tool at aposition 2.0 cm away from one end thereof. The resiliency of the samplewhen the sample was bent at 90° to a curvature radius of 2 cm at aposition 2.0 cm away from the other end of the sample was measured and avalue per 1 cm in width of the sample piece was obtained from this valueand taken as flexural resistance (unit; N/cm).

[0070] 6) Compressive Stress (P3)

[0071] A 2.5 cm×9.0 cm sample piece was bent into two at the center andset in a constant-speed compression tester. The head of the compressiontester was lowered at a rate of 1 cm/min to bend, compress and deformthe sample and measure compression when the sample was compressed to aninterval 3 times its thickness, and a value per 1 cm in width calculatedfrom the measurement value was taken as compression force (unit; N/cm).

[0072] 7) Elastic Recovery (ER)

[0073] A 1 cm (width)×9 cm (length) sample piece was bent into two andplaced under a load of 49.03 N/cm, the load was removed after 1 hour,and the opening angle θ of the sample piece after 30 seconds wasmeasured to obtain elastic recovery from the following equation.

elastic recovery=(θ/180)×100

[0074] 8) Leather-Likeness Index

[0075] This was obtained from the above measurement values of flexuralresistance (RB), compressive stress (P3) and elastic recovery (ER)according to the following equation.

leather-likeness index=P3/(RB×ER)

[0076] 9) Peel Strength (Peel Strength of Surface of Sheet Product)

[0077] This is a value per 1 cm in width of peel strength obtained bylaminating a PVC sheet lined with a plain weave fabric of the same sizeas the sheet on the front side of a 2.5 cm (width)×9.0 cm (length)sample piece by an adhesive (Ulock 420 of Hirono Kagaku Kogyo Co., Ltd.,containing 2 wt % of Coronate L of Nippon Polyurethane Industry Co.,Ltd.) and by making a peel test on this laminate.

[0078] 10) Average Thickness of Adhesive Layer

[0079] The thickness of an adhesive layer was measured at 5 points froma photo of the section of the layer taken by a scanning electronmicroscope and the mean value of these measurement data was taken as theaverage thickness of the adhesive layer.

[0080] 11) Bonding/Non-Bonding Between Elastic Polymer and Fiber

[0081] A photo of the section of a sample was taken by a scanningelectron microscope to observe a space between fibers and the elasticpolymer. Bonding between the elastic polymer (A), the elastic polymer(C) contained in the substrate or the elastic polymer (B) of theadhesive layer and the fiber was observed. When the elastic polymer isadhered to the entire surface of the fiber, it is considered that theelastic polymer is bonded to the fiber. When the area of the space islarger than the section of the fiber, it is considered that the elasticpolymer is not bonded to the fiber even though the elastic polymer iscontacted to part of the fiber.

[0082] 12) Existence of Elastic Polymer in Bundle of Fine Fibers

[0083] When the fiber is a bundle of fine fibers, a photo of the sectionof the fiber is taken by a scanning electron microscope to observe theexistence of the elastic polymer in the bundle of fine fibers. Theexpression “in the bundle of fine fibers” means a space surrounded bythe outermost fine fibers out of a large number of fine fibers producedfrom a single fiber before a fine fiber are made. When the elasticpolymer is existent around the fine fibers and the existence of thefiber before a fine fiber is made cannot be recognized, it is consideredthat the elastic polymer is existent in the bundle of fine fibers.

Reference Example 1 Preparation of Unextracted Sheet (1)

[0084] Nylon-6 and low-density polyethylene were mixed in a ratio of50:50, the obtained mixture was spun into fiber, the fiber was stretchedin a hot water bath at 60° C. to 3 times its original size, mechanicallycrimped and cut to obtain a fiber having a fineness of 4.4 dtex and asize of 51 mm. This fiber was carded, cross layered or needle punched toobtain a needle punched web having a weight of 412 g/m². This web washeated in the chamber of a hot air drier set at 140° C. for 3 minutesand let pass between cooling rolls at 35° C. to prepare a nonwovenfabric (1) having a thickness shown in Table 1. The web weight,thickness and apparent density of the fabric are shown in Table 1.

[0085] Thereafter, an impregnating solution containing 100 parts of adimethylformamide solution (resin concentration of 15%) of apolyether-ester polyurethane resin having a 100% elongation stress of780 N/cm² (corresponding to the elastic polymer (A) or the elasticpolymer (C)), 0.5 part of a hydrophilic coagulation modifier (FG-10 ofMatsumoto Yushi-Seiyaku Co., Ltd.) and 0.5 part of a hydrophobiccoagulation modifier (FG-12 of Matsumoto Yushi-Seiyaku Co., Ltd.) wasprepared. The above nonwoven fabric (1) was immersed in the aboveimpregnating solution, an excess of the impregnating solution wasremoved by squeezing, and the impregnating solution was wet coagulatedin a 15% aqueous solution of dimethylformamide heated at 40° C. Theimpregnated fabric was washed in water and dried to obtain animpregnated substrate (1). The amount of the impregnating resin afterdrying is also shown in Table 1.

[0086] This impregnated substrate (1) was sliced into two sheets at aposition where the thickness was ½. These were designated as unextractedsheets (1).

[0087] As reference data, the physical properties after extraction ofthe sheet (1) were measured. That is, an immersion-nipping step that theunextracted sheet (1) which was not laminated by an adhesive wasimmersed in toluene heated at 850° C. and nipped at an interval whichwas 60% of the thickness of the sheet was repeated to extract and removepolyethylene. This was introduced into hot water heated at 90° C. toremove toluene and dried in the end. The weight, thickness and apparentdensity after extraction of this sheet (1) are shown in Table 1. Thefinal weight after extraction of the sheet (1) was 165 g/m².

Reference Example 2 Preparation of Unextracted Sheet (2)

[0088] The procedure of Reference Example 1 was repeated except that theweb weight was 294 g/m² to obtain a sliced unextracted sheet (2). Theweb weight, thickness and apparent density of a nonwoven fabric and theamount of the impregnating resin after drying of an impregnatedsubstrate are shown in Table 1.

[0089] As reference data, the weight, thickness and apparent densityafter extraction of the sheet (2) were obtained in the same manner as inReference Example 1 and are shown in Table 1. The final weight afterextraction was 132 g/m².

Reference Example 3 Preparation of Unextracted Sheet (3)

[0090] The procedure of Reference Example 1 was repeated except that theweb weight was 572 g/m² to obtain a sliced unextracted sheet (3). Theweb weight, thickness and apparent density of a nonwoven fabric and theamount of the impregnating resin after drying of an impregnatedsubstrate are shown in Table 1.

[0091] As reference data, the weight, thickness and apparent densityafter extraction of the sheet (3) were obtained in the same manner as inReference Example 1 and are shown in Table 1. The final weight afterextraction was 200 g/m².

Reference Example 4 Preparation of Unextracted Sheet (4)

[0092] The procedure of Reference Example 1 was repeated except thatslicing was not carried out to obtain an unextracted sheet (4). The webweight, thickness and apparent density of a nonwoven fabric and theamount of the impregnating resin after drying of an impregnatedsubstrate are shown in Table 1.

[0093] As reference data, the weight, thickness and apparent densityafter extraction of the sheet (4) were obtained in the same manner as inReference Example 1 and are shown in Table 1. The final weight afterextraction was 330 g/m². TABLE 1 R. Ex. 1 R. Ex. 2 R. Ex. 3 R. Ex. 4sheet No. before extraction sheet (1) sheet (2) sheet (3) sheet (4) usednonwoven fabric* web weight (g/m²) 412/2 294/2 572/2 412 thickness (mm)1.33/2 1.43/2 1.25/2 1.33 density (g/cm³) 0.310 0.206 0.458 0.310 amountof impregnating resin 124/2 118/2 114/2 124 (dry)* (g/m²) sliced/notsliced sliced sliced sliced not sliced physical properties of sheet webweight (g/m²) 165 132 200 330 layer after sliced thickness (mm) 0.520.52 0.51 1.00 density (g/cm³) 0.317 0.254 0.392 0.330

Reference Example 5 Preparation of Unextracted Sheet (5) Having a GrainLayer

[0094] A solution containing 100 parts of a dimethylformamide solution(resin concentration of 20%) of a polyether-polyester urethane resinhaving a 100% elongation stress of 1,080 N/cm², 0.5 part of ahydrophilic coagulation modifier (FG-10 of Matsumoto Yushi-Seiyaku Co.,Ltd.) and 0.5 part of a hydrophobic coagulation modifier (FG-12 ofMatsumoto Yushi-Seiyaku Co., Ltd.) was prepared and defoamed to obtain acoating solution having no air bubbles.

[0095] The nonwoven fabric (1) obtained in Reference Example 1 wasimmersed in the impregnating solution prepared in Reference Example 1,an excess of the impregnating solution was removed by squeezing, theabove coating solution was applied to the fabric to a wet weight of 300g/m² and wet coagulated in a 15% aqueous solution of dimethylformamideheated at 40° C. The fabric was washed in water and dried to obtain animpregnated substrate (5) having a grain layer, This substrate wassliced into two sheets at a position where the thickness was ½ and thesesheets were designated as the upper layer and lower layer of theunextracted sheet (5).

[0096] As reference data, the physical properties after extraction ofthe upper layer and lower layer of the sheet (5) were measured. That is,an immersion-nipping step that the unextracted sheets which were notlaminated together yet by an adhesive were immersed in toluene heated at85° C. and nipped at intervals equivalent to 60% of the thickness of thesheet was repeated to remove polyethylene by extraction. This wasintroduced into hot water heated at 90° C. to remove toluene and driedin the end. The thicknesses, weights and apparent densities afterextraction of the upper layer and lower layer of the sheet (5) are shownIn Table 2.

Reference Example 6 Preparation of Unextracted Sheet (6) Having a GrainLayer

[0097] The procedure of Reference Example 5 was repeated except thatslicing was not carried out. The thickness and density of a nonwovenfabric before the impregnation of a resin and the amount of theimpregnating resin are shown in Table 2.

[0098] The impregnated substrate (5) having a grain layer of ReferenceExample 5 was used as an unextracted sheet (6) without slicing.

[0099] As reference data, the thickness, weight and apparent density ofthis sheet after it was extracted directly are shown in Table 2. TABLE 2R. Ex. 5 R. Ex. 5 the upper layer the lower layer R. Ex. 6 sheet No.before extraction the upper layer the lower layer sheet (6) of the sheet(5) of the sheet (5) used nonwoven fabric* web weight (g/m²) 412/2 412/2412 thickness (mm) 1.33/2 1.33/2 1.33 density (g/cm³) 0.310 0.310 0.310amount of impregnating resin 108/2 108/2 108 (dry)* (g/m²) amount ofcoating resin 60 — 60 (dry) (g/m²) sliced/not sliced sliced sliced notsliced physical properties of sheet weight (g/m²) 201 173 375 layerafter extraction thickness (mm) 0.59 0.61 1.13 density (g/cm³) 0.3410.284 0.332

Reference Example 7 Preparation of Unextracted Sheet (7)

[0100] The procedure of Reference Example 1 was repeated except that theweb weight was 420 g/m² to obtain a sliced unextracted sheet (7). Theweb weight, thickness and apparent density of a nonwoven fabric and theamount of an impregnating resin after drying of the impregnatedsubstrate are shown in Table 3.

[0101] As reference data, the weight, thickness and apparent densityafter extraction of the sheet (7) were obtained in the same manner as inReference Example 1 and shown in Table 3. The final weight afterextraction of the sheet was 188 g/m².

Reference Example 8 Preparation of Sheet (8)

[0102] A peel and division type composite fiber which comprisedpolyethylene terephthalate as a first component and nylon-6 as a secondcomponent and had a 16 divided gear-like cross section was melt spun,stretched to 2.0 times in hot water heated at 40° C., mechanicallycrimped and cut to obtain a thermally shrunk, peel and division typecomposite fiber having a fineness of 3.3 dtex, a size of 45 mm and a hotwater shrinkage factor of 9.5%. The volume ratio of the both componentswas 50:50 and each of the both components was divided into 16 segmentsby the other component. This was carded, cross-layered, needle punchedor entangled by a jet stream to obtain a web having a weight of 286g/m². Further, this web was immersed in a hot water tank heated at 75°C. for 20 seconds to shrink a polyethylene terephthalate fiber to reduceits area by 21% and dried with a hot air drier heated at 110° C. toobtain a nonwoven fabric (8) having a thickness shown in Table 3.

[0103] Thereafter, an impregnating solution comprising 100 parts of adimethylformamide solution (resin concentration of 10%) of apolyether-ester polyurethane resin (corresponding to the elastic polymer(A) or the elastic polymer (C)) having a 100% elongation stress of 1,030N/cm², 0.5 part of a hydrophilic coagulation modifier (FG-10 ofMatsumoto Yushi-Seiyaku Co., Ltd.) and 0.5 part of a hydrophobiccoagulation modifier (FG-12 of Matsumoto Yushi-Seiyaku Co., Ltd.) wasprepared. The nonwoven fabric (8) was immersed in the above impregnatingsolution, an excess of the impregnating solution was removed bysqueezing, and the fabric was wet coagulated in a 15% aqueous solutionof dimethylformamide heated at 40° C. This fabric was washed in waterand dried to obtain an impregnated substrate (8). The amount of theimpregnating resin after drying is shown in Table 3.

[0104] This impregnated substrate (8) was sliced into two sheets at aposition where the thickness was ½. The sheets were designated as sheets(8). TABLE 3 R. Ex. 7 R. Ex. 8 sheet No. before extraction sheet (7)sheet (8) used nonwoven fabric* web weight (g/m²) 500/2 362/2 thickness(mm) 1.50/2 1.08/2 density (g/cm³) 0.333 0.335 amount of impregnatingresin 126.2 76/2 (dry)* (g/m²) sliced/not sliced sliced sliced physicalproperties of sheet web weight (g/m²) 313 219 layer after slicedthickness (mm) 0.75 0.54 density (g/cm³) 0.417 0.406 physical propertiesof sheet web weight (g/m²) 188 — layer after extraction thickness (mm)0.61 — density (g/cm³) 0.294 —

Example 1

[0105] An adhesive composition (1) comprising 50 parts of Crisbon TA-290(polyurethane resin of Dainippon Ink and Chemicals, Inc., concentrationof 45%), 50 parts of Crisbon TA-265 (polyurethane resin of Dainippon Inkand Chemicals, Inc., concentration of 65%), 12 parts of Coronate 2094(crosslinking agent of Nippon Polyurethane Industry Co., Ltd.), 3 partsof Crisbon Accel-T (catalyst of Dainippon Ink and Chemicals, Inc.) and20 parts of methyl ethyl ketone was prepared as an adhesive essentiallycomposed of polyurethane resins (corresponding to the elastic polymer(B)). The apparent density of a film formed by applying this adhesivecomposition (1) to release paper, drying and aging was 1.15 g/cm³ and100% elongation stress thereof was 294 N/cm².

[0106] The two sliced unextracted sheets of Reference 1 were used, theadhesive composition (1) was applied to the sliced surface of one ofthem to a wet weight of 200 g/m² which was then placed upon the otherwith the sliced surfaces adjacent to each other and let pass between niprolls arranged at an interval which was 85% of the total thickness ofthe sheets before slicing to be laminated together, and the obtainedlaminate was rolled and aged at 60° C. for 48 hours.

[0107] When the average thickness of the elastic polymer (B) layer wasmeasured, it was 0.06 mm.

[0108] An immersion-nipping step that this sheet was immersed in tolueneheated at 85° C. and nipped at intervals which were 60% of the thicknessof the sheet was then repeated to remove polyethylene contained in thefibers by extraction. This was introduced into hot water heated at 90°C. to remove toluene and dried in the end. The obtained sheet had largeresistance to tension with a shrinkage in width of 3% or less than thatof before extraction and an elongation in length of 2% or less than thatof before extraction and excellent production stability.

[0109] Dimethylformamide was applied to one side of the obtained sheetby a 200-mesh gravure roll, dried and buffed by a polisher having400-mesh emery paper to obtain a napped substrate which was then dyed bya jet dyeing machine.

[0110] The obtained sheet was soft and anti-buckling, had a highleather-likeness index, fine nap on the surface and an excellent writingeffect and was very similar to natural leather nubuck.

[0111] When the sheet was observed through an electron microscope, theelastic polymer (B) penetrated in the sheet layer (1) and the sheetlayer (2) and all the elastic polymers including the elastic polymer (B)were substantially not bonded to the fibers constituting the sheet layer(1) and the sheet layer (2). The bundle of fine fibers penetrated in theelastic material (B) layer but all the elastic polymers including theelastic polymer (B) were not existent in the inside space of the bundleof fine fibers. The elastic polymer (B) was bonded to the elasticpolymers constituting the sheet layers.

[0112] The characteristic property values of the obtained sheet areshown in Table 4.

Examples 2 and 3

[0113] The procedure of Example 1 was repeated except that the twosliced unextracted sheets (2) of Reference Example 2 or the two slicedunextracted sheets (3) of Reference Example 3 were used in place of thetwo unextracted sheets (1) of Reference Example 1.

[0114] When the obtained sheet was observed through an electronmicroscope, the relationship between the elastic polymers and fibersconstituting the sheet layers was the same as in Example 1.

[0115] The characteristic property values of the obtained sheet areshown in Table 4.

Comparative Example 1

[0116] The one unsliced unextracted sheet (4) of Reference Example 4 wasextracted, napped and dyed in the same manner as in Example 1 in placeof the two sliced unextracted sheets (1) of refenrece Example 1 adheredto be used.

[0117] The characteristic property values of the obtained sheet areshown in Table 4.

[0118] Compared with Example 1, the sheet greatly deformed with anelongation in length of 6% and a shrinkage in width of 10% in theextraction step, had no full and tight feel and was inferior in bucklingresistance and leather-likeness index though it was soft. TABLE 4 Ex. 1Ex. 2 Ex. 3 C. Ex. 1 sheet weight (upper layer + lower layer) g/m² 165 +165 132 + 132 200 + 200 330 layer density ratio ρ1/ρ2 1.00 1.00 1.00 —adhesive 100% elongation stress of film N/cm² 294 294 294 — layer amountof coating (dry weight) g/m² 80 80 80 — average thickness mm 0.06 0.060.06 — leather- thickness mm 1.05 1.05 1.03 1.00 like weight g/m² 410.0330.0 480.0 330.0 sheet density g/cm³ 0.390 0.314 0.466 0.330 product 5%stress (δ5) length N/cm 3.23 3.43 2.35 1.67 width N/cm 1.96 1.96 1.471.47 20% stress (δ20) length N/cm 20.87 29.11 17.64 11.27 width N/cm14.50 10.19 9.51 8.33 tensile strength length N/cm 124.46 114.66 138.18111.72 width N/cm 110.74 105.84 129.36 86.24 flexural resistance (RB)length N/cm 0.0024 0.0029 0.0020 0.0026 compressive stress (P3) lengthN/cm 0.21 0.23 0.24 0.11 elastic recovery (ER) length % 80.0 80.7 78.087.0 leather-likeness index P3/(RB · ER) 1.11 0.95 1.54 0.47 δ20/δ5length 6.5 8.5 7.5 6.8 width 7.4 5.2 6.5 5.7 peel strength N/cm 25.527.5 24.5 25.5 bonding between elastic polymer no bonding no bonding nobonding (no bonding)* and fibers existence of elastic polymer in bundlenot not not (not of fine fibers existent existent existent existent)*

Example 4

[0119] An adhesive composition (2) comprising 30 parts of Crisbon TA-290(polyurethane resin of Dainippon Ink and Chemicals, Inc., concentrationof 45%), 30 parts of Crisbon TA-265 (polyurethane resin of Dainippon Inkand Chemicals, Inc., concentration of 65%), 40 parts of Crisbon NB-765(polyurethane resin of Dainippon Ink and Chemicals Inc., concentrationof 30%), 10 parts of Coronate 2094 (crosslinking agent of NipponPolyurethane Industry Co., Ltd.), 3 parts of Crisbon Accel-T (catalystof Dainippon Ink and Chemicals, Inc.) and 20 parts of methyl ethylketone was prepared as an adhesive essentially composed of polyurethaneresins (corresponding to the elastic polymer (B)). The 100% elongationstress of a film formed by applying this adhesive composition (2) torelease paper, drying and aging was 588 N/cm². The laminate was obtainedin the same manner as in Example 1 except that the unextracted sheet (3)of Reference Example 3 as an upper layer and the unextracted sheet (4)of Reference Example 4 as a lower layer were laminated together by theabove adhesive composition (2), and the obtained laminate was extracted,napped and dyed.

[0120] When the obtained sheet was observed through an electronmicroscope, the relationship between the elastic polymers and fibersconstituting the sheet layers was the same as in Example 1.

[0121] The obtained sheet was anti-buckling and had a highleather-likeness index and was therefore excellent as a material forshoes. The characteristic property values of the obtained sheet areshown in Table 5.

Example 5

[0122] An adhesive composition (3) comprising 15 parts of Crisbon TA-290(polyurethane resin of Dainippon Ink and Chemicals, Inc., concentrationof 45%), 15 parts of Crisbon TA-265 (polyurethane resin of Dainippon Inkand Chemicals, Inc., concentration of 65%), 80 parts of Crisbon NB-765(polyurethane resin of Dainippon Ink and Chemicals Inc., concentrationof 30%), 8 parts of Coronate 2094 (crosslinking agent of NipponPolyurethane Industry Co., Ltd.), 3 parts of Crisbon Accel-T (catalystof Dainippon Ink and Chemicals, Inc.) and 20 parts of methyl ethylketone was prepared as an adhesive essentially composed of polyurethaneresins (corresponding to the elastic polymer (B)). The 100% elongationstress of a film formed by applying this adhesive composition (3) torelease paper, drying and aging was 883 N/cm².

[0123] The laminate was obtained in the same manner as in Example 1except that the unextracted sheet (3) of Reference Example 3 as an upperlayer and the unextracted sheet (4) of Reference Example 4 as a lowerlayer were laminated together by the above adhesive composition (3), andthe obtained laminate was extracted, napped and dyed.

[0124] When the obtained sheet was observed through an electronmicroscope, the relationship between the elastic polymers and fibersconstituting the sheet layers was the same as in Example 1.

[0125] The obtained sheet was anti-buckling and had a highleather-likeness index and was therefore excellent as a material forshoes. The characteristic property values of the obtained sheet areshown in Table 5.

Example 6

[0126] The procedure of Example 1 was repeated except that theunextracted sheet (3) of Reference Example 3 was used as an upper layerand the unextracted sheet (2) of Reference Example 2 was used as a lowerlayer in place of the two unextracted sheets (1) of Reference Example 1.The average thickness of the elastic polymer (B) layer was 0.08 mm, andthe obtained sheet had a fine nubuck-like surface appearance and wasvery soft and suitable for use in shoes and furniture as a leather-likesheet product. When it was observed through an electron microscope, therelationship between the elastic polymers and fibers constituting thesheet layers was the same as in Example 1. The characteristic propertiesof the obtained sheet are shown in Table 5.

Example 7

[0127] The procedure of Example 6 was repeated except that an adhesivecontaining air bubbles was prepared by stirring at a high speed at thesame time of blowing air into an adhesive composition with using an airfoamer and was used in place of the adhesive composition (1). Theaverage thickness of the elastic polymer (B) layer was 0.10 mm and theapparent density of a sheet formed only from this adhesive containingair bubbles was 0.6 g/cm³. When the sheet was observed through anelectron microscope, the relationship between the elastic bodies andfibers constituting the sheet layers was the same as in Example 1. Thecharacteristic properties of the obtained sheet are shown in Table 5.

Example 8

[0128] The procedure of Example 6 was repeated except that a sheethaving a thickness of 0.45 mm and a substrate density of 0.44 g/cm³ wasformed by processing the unextracted sheet (3) of Reference Example 3with a press roll heated at 100° C. and used as an upper layer in steadof using the unextracted sheet (3) of Reference Example 3 directly. Theobtained sheet had slight surface hardness but was anti-buckling and wasexcellent as a material for shoes. When it was observed through anelectron microscope, the relationship between the elastic polymers andfibers constituting the sheet layers was the same as in Example 1. Thecharacteristic properties of the obtained sheet are shown in Table 5.TABLE 5 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 sheet weight (upper layer + lowerlayer) g/m² 200 + 330 200 + 330 200 + 132 200 + 132 200 + 132 layerdensity ratio ρ1/ρ2 1.19 1.19 1.54 1.54 1.75 adhesive 100% elongationstress of film N/cm² 588 833 294 294 294 layer amount of coating (dryweight) g/m² 120 118 100 60 98 average thickness mm 0.16 0.15 0.08 0.100.08 leather- thickness mm 1.60 1.60 1.11 1.12 1.05 like weight g/m²650.0 648.0 432.0 392.0 430.0 sheet density g/cm³ 0.406 0.405 0.3890.350 0.410 product 5% stress (δ5) length N/cm 5.19 5.68 3.14 2.74 3.43width N/cm 2.94 3.43 2.35 2.16 2.74 20% stress (δ20) length N/cm 43.6145.08 27.44 25.48 28.42 width N/cm 15.29 16.17 13.72 13.52 14.70 tensilestrength length N/cm 160.72 163.66 156.80 153.86 154.84 width N/cm154.84 159.74 150.92 149.94 150.92 flexural resistance (RB) length N/cm0.0073 0.0078 0.0039 0.0036 0.0047 compressive stress (P3) length N/cm0.40 0.44 0.25 0.23 0.31 elastic recovery (ER) length % 80.7 80.0 80.079.0 79.0 leather-likeness index P3/(RB · ER) 0.69 0.70 0.78 0.79 0.84δ20/δ5 length 8.4 7.9 8.8 9.3 8.3 width 5.2 4.7 5.8 6.3 5.4 peelstrength N/cm 24.5 24.5 27.5 19.6 27.5 bonding between elastic polymerno bonding no bonding no bonding no bonding no bonding and fibersexistence of elastic polymer in bundle not not not not not of finefibers existent existent existent existent existent

Example 9

[0129] Bonding and extraction were carried out in the same manner as inExample 1 except that the two sliced unextracted sheets (5) of ReferenceExample 5 were used in place of the two sliced unextracted sheets (1) ofReference Example 1.

[0130] The obtained sheet had large resistance to tension with ashrinkage in width of 3% or less and an elongation in length of 2% orless in the extraction step and had excellent production stability.

[0131] The surface having coating layer of the obtained sheet wasembossed to provide a grain pattern, the surface finished with apolyurethane resin having a 100% elongation stress of 392 N/cm² by a200-mesh gravure roll and rubbed after adding a softening agent.

[0132] When the obtained sheet was observed through an electronmicroscope, the relationship between the elastic polymers and fibersconstituting the sheet layers was the same as in Example 1.

[0133] The obtained sheet having a grain layer was soft andanti-buckling, had a high leather-likeness index, finely wrinkles on thesurface when it was bent and was very similar to natural leather havinga high-grade grain layer. The characteristic property values of theobtained sheet are shown in Table 5.

Comparative Example 2

[0134] Extraction and subsequent steps were carried out in the samemanner as in Example 9 except that one unsliced unextracted sheet (6) ofReference Example 6 was used in place of the two sliced unextractedsheets (5) of Reference Example 5 adhered to be used. The thickness anddensity of a non-woven fabric before the impregnation of a resin, theamount of the impregnating resin, and the thickness, weight and apparentdensity after extraction of the fabric are shown in Table 6. Thecharacteristic property values of the finally obtained sheet are shownin Table 6.

[0135] The obtained sheet having a grain layer greatly deformed with ashrinkage in width of 10% or more and an elongation in length of 7.% inthe extraction step compared with Example 9, was very soft without afull and tight feel and inferior in anti-buckling and leather-likenessindex. The sheet was inferior as a sheet having a grain layer becauselarge wrinkles were formed on the surface when it was bent. Thecharacteristic property values of this sheet are shown in Table 6.

Example 10

[0136] The same adhesive composition (1) as in Example 1 was applied tothe sliced surface of the sheet (8) (corresponding to the sheet layer(2)) obtained in Reference Example 8 to a wet weight of 230 g/m², andthe sheet (8) was placed upon the sliced surface of the unextractedsheet (7) (corresponding to the sheet layer (1)) obtained in ReferenceExample 7 and laminated together in the same manner as in Example 1. Theaverage thickness of the adhesive layer was 0.07 mm. Polyethylene wasremoved from this substrate by extraction with toluene heated at 85° C.in the same manner as in Example 1. The obtained substrate had largeresistance to tension with a shrinkage in width of 3% or less and anelongation in length of 2% or less in the extraction step and hadexcellent production stability.

[0137] Dimethylformamide was applied to the surface corresponding to thesheet layer (1) (unextracted sheet (7)) of the obtained sheet by a200-mesh gravure roll, dried and buffed by a polisher having 400-meshemery paper to form a napped substrate which was then dyed by a jetdyeing machine.

[0138] The obtained sheet was soft and anti-buckling, had a highleather-likeness index, fine nap on the surface and an excellent writingeffect, and was similar to natural leather nubuck.

[0139] When the obtained sheet was observed through an electronmicroscope, the elastic polymer (B) penetrated in the sheet layer (1)and the sheet layer (2) and the elastic polymer (A) and the elasticpolymer (B) were substantially not bonded to the fibers constituting thesheet layer (1). The bundle of fine fibers constituting the sheet layer(1) penetrated in the elastic polymer (B) but the elastic polymer (A)and the elastic polymer (B) were not existent in the inside space of thebundle of fine fibers. The elastic polymer (B) was bonded to the elasticpolymers constituting the sheet layers.

[0140] The characteristic property values of the obtained sheet areshown in Table 6. TABLE 6 Ex. 9 C. Ex. 2 Ex. 10 sheet weight (upperlayer + lower layer) g/m² 201 + 173 375 188 + 219 layer density ratiop1/p2 1.20 — 0.72 adhesive 100% elongation stress of film N/cm² 294 —294 layer amount of coating (dry weight) g/m² 58 — 80 average thicknessmm 0.06 — 0.07 leather- thickness mm 1.23 1.13 1.15 like weight g/m²432.0 375.0 487.0 sheet density g/cm³ 0.351 0.332 0.423 product 5%stress (δ5) length N/cm 3.52 1.53 4.02 width N/cm 2.23 1.45 3.75 20%stress (δ20) length N/cm 21.22 12.23 22.45 width N/cm 15.37 8.89 18.79tensile strength length N/cm 131.24 121.32 145.30 width N/cm 123.2187.24 136.20 flexural resistance (RB) length N/cm 0.0024 0.0023 0.0026compressive stress (P3) length N/cm 0.22 0.10 0.22 elastic recovery (ER)length % 78.0 87.0 77.6 leather-likeness index P3/(RB · ER) 1.18 0.501.09 δ20/δ5 length 6.0 8.0 5.6 width 6.9 6.1 5.0 peel strength N/cm 24.525.5 24.7 bonding between elastic polymer no bonding (no bonding)*1 nobonding (B layer)*2 and fibers existence of elastic polymer in bundlenot (not not existent (upper layer) of fine fibers existent existent)*1existent (lower layer)*2

[0141] * 1; Comparative Example 2 had no adhesive layer.

[0142] * 2; The elastic polymers were not existent in a bundle of finefibers of the upper layer corresponding to the sheet layer (1) and theelastic polymer (B) and the elastic polymer (A) were not bonded to thefibers. However, the bundle of fine fibers of the lower layercorresponding to the sheet layer (2) could not be recognized, theelastic polymer (C) was existent around the fine fibers, and the elasticpolymer (B) and the elastic polymer (C) were bonded to the fibers.

EFFECT OF THE INVENTION

[0143] According to the present invention, there is obtained aleather-like sheet product which has good balance between softness andbuckling resistance like natural leather and is deformed round with finewrinkles when it is bent. According to the production process of thepresent invention, shrinkage in width can be suppressed in theproduction process, thereby making it easy to produce a product having alarge width.

1. A leather-like sheet product comprising (a) a sheet layer (1)composed of a fiber assembly (1) of fine fibers and an elastic polymer(A) existent in a space between fibers of the fiber assembly (1), (b) asheet layer (2) essentially composed of a fiber assembly (2) or composedof a fiber assembly (2) and an elastic polymer (C) existent in a spacebetween fibers of the fiber assembly (2), and (c) an adhesive layer,composed of an elastic polymer (B), for bonding together the sheet layer(1) and the sheet layer (2), wherein (d) the fibers of the sheet layer(1) and the fibers of the sheet layer (2) penetrate in the adhesivelayer at the respective interfaces, the fibers of the sheet layer (1)are existent in the adhesive layer in a state that they aresubstantially not bonded to the elastic polymer (B), and the fibers ofthe sheet layer (2) are existent in the adhesive layer in a state thatthey are substantially bonded or not bonded to the elastic polymer (B);and (e) the elastic polymer (B) is existent in the adhesive layer in astate that it is bonded to at least the elastic polymer (A) contained inthe sheet layer (1) at the interface.
 2. The leather-like sheet productof claim 1, wherein the fine fibers are existent as a bundle of finefibers in the sheet layer (1), the bundle of fine fibers penetrates inthe adhesive layer at the interface of the sheet layer (1), and theelastic polymer (B) as the component of the adhesive layer issubstantially not existent in the inside space of the bundle of finefibers.
 3. The leather-like sheet product of claim 1, wherein theadhesive layer is bonded to the elastic polymer (A) at the interface ofthe sheet layer (1).
 4. The leather-like sheet product of claim 1,wherein the sheet layer (2) is composed of the fiber assembly (2) andthe elastic polymer (C) existent in a space between fibers of the fiberassembly.
 5. The leather-like sheet product of claim 4, wherein thesheet layer (2) is composed of fine fibers and the elastic polymer (C)is existent in a space between the fibers.
 6. The leather-like sheetproduct of claim 4, wherein the adhesive layer is bonded to the elasticpolymer (C) at the interface of the sheet layer (2).
 7. The leather-likesheet product of any one of claims 1 to 6, wherein the elastic polymer(B) of the adhesive layer is substantially not bonded to the fibersconstituting the sheet layer (2) at the interface of the sheet layer(2).
 8. The leather-like sheet product of claim 1, wherein the apparentdensity ρ₁ (g/cm³) and thickness t₁ (mm) of the sheet layer (1) and theapparent density ρ₂ (g/cm³) and thickness t₂ (mm) of the sheet layer (2)satisfy the following expressions (1) to (6) at the same time:0.20≦ρ₁≦0.48  (1) 0.20≦ρ₂≦0.48  (2) 0.5≦ρ₁/ρ₂≦2.4  (3) 0.2≦t₁≦1.5  (4)0.2≦t₂≦2.5  (5) 0.4≦(t ₁ +t ₂)≦4.0  (6).
 9. The leather-like sheetproduct of claim 1, wherein the average thickness of the adhesive layeris 0.01 to 0.5 mm.
 10. The leather-like sheet product of claim 1,wherein the 100% elongation stress of a film formed only from theelastic polymer (B) of the adhesive layer is 200 to 3,000 N/cm².
 11. Theleather-like sheet product of claim 8 which has a leather-likeness indexof 0.5 to 2.0.
 12. The leather-like sheet product of claim 1, whereinthe surface of the sheet product has a peel strength of 20 N/cm or more.13. A leather-like sheet product comprising (a) a sheet layer (1)composed of a fiber assembly (1) of fine fibers and an elastic polymer(A) existent in a space between fibers of the fiber assembly (1), (b) asheet layer (2) composed of a fiber assembly (2) of fine fibers and anelastic polymer (C) existent in a space between fibers of the fiberassembly (2), and (c) an adhesive layer, composed of an elastic polymer(B), for bonding together the sheet layer (1) and the sheet layer (2),wherein (d) the fibers of the sheet layer (1) and the fibers of thesheet layer (2) penetrate in the adhesive layer at the respectiveinterfaces, the fibers of the sheet layer (1) are existent in theadhesive layer in a state that they are substantially not bonded to theelastic polymer (B), and the fibers of the sheet layer (2) are existentin the adhesive layer in a state that they are substantially not bondedto the elastic polymer (B); and (e) the elastic polymer (B) is existentin the adhesive layer in a state that it is bonded to the elasticpolymer (A) contained in the sheet layer (1) at the interface and to theelastic polymer (C) contained in the sheet layer (2) at the interface.14. A leather-like sheet product comprising (a) a sheet layer (1)composed of a fiber assembly (1) of fine fibers and an elastic polymer(A) existent in a space between fibers of the fiber assembly (1), (b) asheet layer (2) composed of a fiber assembly (2) of fine fibers and anelastic polymer (C) existent in a space between fibers of the fiberassembly (2), and (c) an adhesive layer, composed of an elastic polymer(B), for bonding together the sheet layer (1) and the sheet layer (2),wherein (d) the fibers of the sheet layer (1) and the fibers of thesheet layer (2) penetrate in the adhesive layer at the respectiveinterfaces, the fibers of the sheet layer (1) are existent in theadhesive layer in a state that they are substantially not bonded to theelastic polymer (B), and the fibers of the sheet layer (2) are existentin the adhesive layer in a state that they are substantially bonded tothe elastic polymer (B); and (e) the elastic polymer (B) is existent inthe adhesive layer in a state that it is bonded to at least the elasticpolymer (A) contained in the sheet layer (1) at the interface and to theelastic polymer (C) contained in the sheet layer (2) at the interface.15. A process for producing a leather-like sheet product comprising thesteps of: bonding together a sheet layer (1′) composed of a fiberassembly of sea-island type fibers made from a mixture of at least twodifferent polymers which differ from each other in solvent solubilityand an elastic polymer (A) existent in a space between fibers of thefiber assembly and a sheet layer (2) essentially composed of a fiberassembly (2) or composed of a fiber assembly (2) and an elastic polymer(C) existent in a space between fibers of the fiber assembly (2) by anadhesive layer composed of an elastic polymer (B); and treating thelaminated sheets with a solvent which does not dissolve the islandcomponent of the sea-island type fiber and the elastic polymers butdissolves the sea component of the sea-island type fiber to dissolve andremove the sea component in order to make a fine fiber from thesea-island fiber.
 16. The leather-like sheet product production processof claim 15, wherein the sheet layer (2) is composed of fine fibers andthe elastic polymer (C) existent in a space between the fibers.
 17. Theleather-like sheet product production process of claim 15, wherein thesheet layer (2) is composed of sea-island type fibers made from amixture of at least two different polymers which differ from each otherin solvent solubility and the elastic polymer (C) existent in a spacebetween the fibers.
 18. Artificial leather comprising the leather-likesheet product of claim 1, 13 or 14.